This invention relates to electronic control system method and means to provide for optimum induction motor operating efficiency over a wide range of motor speeds and torques.
Typically, induction motors are designed for optimum operating efficiency at some given, or normal, operating speed and load. For variable speed operation and varying torque requirements, the a-c frequency and voltage supplied to the motor windings may be controlled so as to optimize certain operating characteristics over a range of motor load and speed requirements. Numerous such arrangements are known as shown, for example, in U.S. Pat. Nos. 3,896,356; 3,860,858; 3,851,234; and 3,863,121. However, prior art arrangements often employ special speed, torque or angle sensing devices for use in the control circuitry which devices add considerable expense to the system.